New member with a question. I am restoring a Cub with no serial number plate. Engine casting is 10 26 W, which I think can be a 51 or 73. Engine serial number is 1MCUBM 23209. What year do I have?? Thanks in advance.

launchba wrote:New member with a question. I am restoring a Cub with no serial number plate. Engine casting is 10 26 W, which I think can be a 51 or 73. Engine serial number is 1MCUBM 23209. What year do I have?? Thanks in advance.

No missing numbers. Your engine is not original to the tractor, it was originally installed in a combine or bailer. These engines did not use the same SN sequence as that of the tractors, so that is why your 1951 cast code engine has a shorter SN than one originally installed on a 1951 tractor. The PN on the engine should be 251341R6. By 1973, IH was well into R8 revisions on blocks.